Fixed throttle torque demand strategy

Abstract

This invention teaches operating a vehicle with a fixed throttle by determining a modified torque which is determined as a function of driver demand torque. Such modified torque is used to determine the amount spark retard or fuel cut-out required to achieve the demanded torque.

We claim: 
     
       1. A method for operating an internal combustion engine having a fixed throttle including the steps of: determining a desired driver engine torque;   determining a maximum available engine torque;   controlling engine torque as a function of the ratio of a desired engine torque to a maximum available engine torque;   sensing engine speed, throttle angle, exhaust gas recirculation, intake air temperature, and accelerator pedal position;   developing signals representing engine speed, throttle angle, exhaust gas recirculation, intake air temperature, and accelerator pedal position;   calculating the maximum available engine load;   calculating the maximum available engine torque using engine load and engine speed;   determining desired driver demand engine torque as a percentage of the maximum torque available; and   reducing actual engine torque to desired engine torque by retarding spark advance and cutting out fuel injector operation.   
     
     
       2. A method as recited in claim 1 further including the step of determining the maximum available engine torque by: estimating the maximum available torque using a stored sea level load function, actual engine speed, actual EGR flow, actual air charge temperature, and inferred barometric pressure.   
     
     
       3. A method as recited in claim 2 further comprising the steps of: calculating desired torque by determining a net torque by subtracting an engine torque loss from maximum available torque at the fixed throttle condition, such net torque being then multiplied by a calibration function indicating a desired torque percentage, so that the percentage of desired torque with respect to maximum torque is determined as a function of the percentage of foot angle indicating accelerator position; and   sending a driver requested engine torque to a torque control module, where a number of cylinders to be turned off is determined and spark advance reduction is calculated and implemented.   
     
     
       4. A method for operating an internal combustion engine including the steps of: determining the throttle is in a fixed position;   sensing the following inputs:   ______________________________________                                    
ACT            air charge temperature                                     
BP             barometric pressure                                        
N              engine speed                                               
ETP.sub.-- rel tp.sub.-- rel of electronic throttle                       
EGRACT         actual egr rate                                            
IAC            intake runner control state                                
TQ.sub.-- LOSS tp losses for inferred tq                                  
% FA           percent foot angle;                                        
______________________________________                                    
       determining the following calibration parameters:   ______________________________________                                    
FN059           temperature compensation for                              
                inferred bp                                               
FN1036A         load at sea level for n vs                                
                tp.sub.-- rel                                             
FN1036B         load at sea level for n vs                                
                tp.sub.-- rel, secondarys open                            
FN1037          load from egr, n vs tp.sub.-- rel                         
FN1615A         indicated engine torque, n vs                             
                load                                                      
FN0ETC.sub.-- FMEM                                                        
                driver dem and transfer                                   
                function, percentage of torque                            
                available; and                                            
______________________________________                                    
       generating the following outputs in accordance with the following equations:   ______________________________________                                    
max.sub.-- av.sub.-- load                                                 
               maximum load available for a                               
               fixed ECT position                                         
max.sub.-- av.sub.-- tq                                                   
               maximum tq available for a                                 
               fixed ETC position                                         
da.sub.-- tq.sub.-- fmem                                                  
               driver requested engine torque                             
               for FMEM situation                                         
______________________________________                                    
     if the state of IAC equals "1", then determining:     ______________________________________                                    
max.sub.-- av.sub.-- load =                                               
                  [fn1036b(n,etp.sub.-- rel) -                            
                  egract/10 *                                             
                  fn1037(n,etp.sub.-- rel)]                               
                  * fn059(act)*bp/29.92                                   
______________________________________                                    
     if the state of IAC does not equal "1", then determining:     ______________________________________                                    
max.sub.-- av.sub.-- load =                                               
                [fn1036a(n,etp.sub.-- rel) -                              
                egract/10 * fn1037(n,etp.sub.-- rel)]                     
                * fn059(act)*bp/29.92                                     
______________________________________                                    
     calculating maximum available torque using:     max.sub.-- av.sub.-- tq=fn1615a(n,max.sub.-- av.sub.-- laod)     calculating desired torque using:     ______________________________________                                    
da.sub.-- tq.sub.-- fmem =                                                
                [max.sub.-- av.sub.-- tq -                                
                tq.sub.-- loss]*fn0etc.sub.-- fmem(% fa)                  
______________________________________                                    
     thereby calculating desired torque by determining a net torque by subtracting an engine torque loss from maximum available torque at the fixed throttle condition, such net torque being then multiplied by a calibration function indicating a desired torque percentage, so that the percentage of desired torque with respect to maximum torque is determined as a function of the percentage of a foot angle indicating accelerator position; and     sending da --  tq --  fmem to a torque control module, where a number of cylinders to be turned off is determined and spark advance reduction is calculated and implemented.